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Re: Coaxing N[] to work

  • To: mathgroup at smc.vnet.net
  • Subject: [mg73412] Re: Coaxing N[] to work
  • From: dh <dh at metrohm.ch>
  • Date: Thu, 15 Feb 2007 05:11:34 -0500 (EST)
  • References: <equo6r$in0$1@smc.vnet.net>


Hi,

N can not create additional precission. You calculated lambda with 

machine precission!

Daniel



p at dirac.org wrote:

> Sometimes N[,] doesn't appear to work.  Like here:

> 

> 

> x = {2.0, 3.0, 5.0};

> A = { {6.0, 2.0, 1.0}, {2.0, 3.0, 1.0}, {1.0, 1.0, 1.0} };

> For[ k=0, k<15, ++k,

>    lambda = x.A.x/(x.x);

>    y = LinearSolve[A,x];

>    x = y / Norm[y,Infinity];

> ]

> N[lambda, 30]

> 

> 

> The output is:

> 

>    Out[5]= 0.578933

> 

> I was expecting 30 digits.  Why did N[] ignore my request for 30 digits?

> 




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